This invention relates to a cutter for use in a double-pile loom.
In a double-pile loom, the top and the bottom ground fabrics are doubly woven and pile yarns are inserted therein. When these pile yarns are cut at the rear of the cloth fell and turned into piles, two separate cut warp pile fabric are simultaneously produced.
These kinds of pile fabrics are called wilton, moquette, velvet, plush etc.
As in an ordinary loom such as a plain-loom, the double-pile loom is comprised of warpletting-off apparatus, shedding apparatus, weft inserting apparatus, beeting apparatus, taking-up apparatus and so on.
However the double-pile loom is different from ordinary looms for weaving cotton or woolen fabric since it includes a pile cutting apparatus.
As regards the fabric woven by the ordinary loom, the appearance of a woven texture composed of warps and wefts intersecting each other is a decisive factor for determining the commercial value of the fabric. An uneven weft density or skew (wefts running not straight) is regarded as a defect.
In a pile fabric, woven texture composed of warps and wefts intersecting esch other are not apparent on the right side of the fabric and less influential upon the commercial value thereof but, instead, smoothness (evenness) of the pile-covered surface is an important factor decisive to the commercial value thereof. Roughness of this surface caused by pile lengh difference is considered a defect.
The degree of smoothness of pile-covered surface depends on whether the cutting apparatus operates regularly or not.
A cutting apparatus known in the prior art, has the structure as shown in FIGS. 1 through 4.
In the drawings, the reference numerals 18 and 19 indicate the ground texture of the top and the bottom fabrics composed of warps and wefts. The numeral 14 indicates pile yarns which are woven into the structure so as to stitch the ground texture 18 and 19 of the top and the bottom fabrics to each other. The numerals 2 and 3 indicate a rail supported in parallel with the cloth fell and a slider sliding on the rail 2 and provided with a cutter 4, respectively. The slider is driven to reciprocate in the space between the top and the bottom ground textures 18 and 19, respectively, by a drum 6, which turns in the right and the reverse directions synchronously with a picking motion, via rope 5.
The cutter edge 13 cuts a multitude of pile yarns 14 woven into the texture and stitching the top and the bottom ground textures 18 and 19, respectively, and arranged in a line weftwise for formation of piles 15 in line weftwise. At the same time, the ground textures 18 and 19 are separated from each other above and below. Two cut warp pile fabrics are thus formed--the top fabric 11 with the pile-covered surface on the lower side, and the bottom fabric 12 with a similar pile-covered surface on the upper side.
The numerals 9 and 10 denote stationary platelike blocks called scale for preventing the top and the bottom ground textures 18 and 19, respectively, from vibrating while the cutter 4 travels.
Usually, the number of pile yarns lined weftwise reaches thousands and the cutter edge 13 to cut these yarns in single stroke is susceptible to wear. As a countermeasure to such wear as above, a pair of grindstones 7 and 8 (7' and 8') directed upward and downward, respectively, are disposed near both edges of the fabric and energized by springs 16 (16') so that the obverse and the reverse sides of the running cutter edge 13 are ground by the grindstones during every reciprocation thereof.
To grind the cutter edge at a fixed angle from end to end thereof, grindstones 7 and 8 (7' and 8') must be under a fixed uniform pressure while touching the cutter edge from end to end thereof.
In other words, grindstones must be positioned and mounted on the loom so that the cutter edge is in point-contact with the grindstones under a fixed pressure. The grindstones surface in contact with the cutter edge must be curved in the lengthwise direction like the surface of a cone but straight in the transverse derection at any position from end to end thereof along the cutter running direction, and these conditions must be invariably maintained.
Such, performance however, is possible in theory but extremely difficult in practice.
Such problems as above involved in the prior art are summarized as follows:
(1) Pressing action by the weight of the downward directed grindstone 8 upon the cutter edge 13 is strong whereas that by the upward directed one 7 is weak. Accordingly, in consideration of the weight of the grindstones, the force of a spring 16 for the downward directed grindstone 7 and that of another spring 16' for the upward directed grindstone 8 must be weak and strong, respectively, for pressing both grindstones to the cutter edge 13 with the same degree of pressure. However, designing spring 16 and 16' to meet such requirement is difficult. Thus the cutter edge gradually varies in the shape while used such that, the obverse and the reverse sides (upside and downside) of the cutting edge lose angular therebetween, and a pile length difference is caused between both sheets of fabric in such a way that the pile length a of the fabric on one side to which the cutter edge is deviated is short whereas pile length b on the other side is long. Although the fabric having long piles can be correctly finished by shearing and adapted to conform to the standard, that having short piles cannot but be disposed of as rejected.
(2) By adjusting the positions of the scales 9 and 10 in the vertical direction for setting a path on which the cutter edge 13 runs at a middle position between the top fabric 11 and the bottom fabric 12, an inferior product having a length difference between piles 15 of the top fabric 11 and the bottom fabric 12 is prevented. However, such adjustment if performed every time required, gradually cause the middle position between the top fabric 11 and the bottom one 12 to deviate. In this case, a new cutter edge replacing the old one runs on an unexpected course, whereby a large pile length difference is caused between the top and the bottom fabrics, and a sharp step appear on the pile-covered surface of either sheet of the fabric correspondingly to the time of the replacement of cutter edge. Above all, in the case of moquette, since the pile length thereof a (b) is usually as short as 2 to 3 mm, the cutter edge, when deviated, may possibly eat into the ground texture 18 (19) on one side and produce an un-repairable defect.
(3) The cutter gradually becomes short since the edge thereof is always subjected to grinding by the grindstones. The edge 13' of a new cutter replacing the old one is located close to the cloth fell in length d anticipated to be worn out. Accordingly, althought one row of pile yarns lined weftwise will have been cut by one stroke of the cutter, two or more rows are unreasonably cut immediately after the replacement of cutters. Variation in cutting conditions as above causes a defect called weftwise streak on the pile-covered surface.
(4) Grindstones 7 and 8 are liable to be subjected to strong pressing to the cutter edge 13 due to the user's desire to obtain sharp cutting, however, extremely strong pressing causes the cutter edge 13 to be too sharp and prouce a burr on the edge 13, thereby reducing cutting ability. Moreover, the cutter edge thus deteriorated tears the pile yarns and causes an un-repairable hairy surface.
(5) A step-like rubbing mark gradually appears on the grindstones at the part rubbed by the cutter edge. When the cutter is replaced and positionally adjusted without replacing the transformed grindstones, transformation of the cutter edge, above all burr, is expedited. Therefore, even when either a cutter or a grindstone is worn and transformed, both of them must be replaced, or ground and adjusted correctly. However, grinding and adjustment of the worn grindstones requires a considerable level of skill and, in many cases, the worn grindstone is must be replaced by a new one.
(6) In the case of the fabric of high pile-density such as moquette, a pile length difference as small as 0.1 mm is regarded as a defect known as a stepped surface. Adjustment of the scales 9 and 10, grindstones 7 and 8, and cutter edge 13 requires a high level of skill and a considerable length of time. Further, as a matter of practice, the cutter edge must be ground and adjusted at intervals of about 30 min. during weaving. Therefore, the conventional cutting apparatus makes complete automation of the double-pile loom impossible, leaving the loom at a markedly low level of productivity.
(7) Trial operation is required after fine adjustment of the replaced cutter or grindstones and inevitably causes clumsily cut yarn.
(8) As described above, a step-like mark resulting from pile length difference as small as 0.1 mm is distinguished as a defect and this defect is inevitable even if a considerably high level of skill is applied to operation. Therefore, according to the prior art, the fabric is woven so as to be provided with piles slightly longer than those to be obtained in the finals in consideration of occurrence of such defect as above and then the piles are evenly cut by shearing to be conformable to the standard length.
Usually, the tip of pile in length as 0.3 to 0.6 mm is cut away by shearing. However, removal as much as 0.3 to 0.6 mm from the pile length of the short-pile fabric such as a moquette which ranges from 2 to 3 mm corresponds to a 15 or more percent loss of pile yarn. And, the pile yarn costs far higher than the warp and the weft yarns for the ground texture. Thus, loss of yarn in the shearing process adds greatly to the cost of products.